New to the fitness thing!

Hey! So I just turned 32, 5'3", and currently 136.

I've sent most of my life trying to gain weight, never losing. I've no idea on where to start, and most that I Google seems like a gimmick. I bought a galaxy watch for my birthday, and am starting with a 1,200/day calorie diet and trying to be active.

I don't have any idea how to work out in a gym, but would like to. I don't understand all of the dynamics to losing weight and being fit, but am trying to learn. I just started running a lot, and gave myself a stress fracture in my leg sooooo plan B. So far that consists of walking, but I want to do more.

I can use some friends, encouragement, and advice!